A:
B:
C:
D:
如图,在△ABC中,BC=6,M、N分别是AB、AC的中点,则MN等于( )
Finding information in today's world is easy. The is how you can tell if the information you get is useful or not.
物体做匀加速直线运动,其加速度的大小为2m/s2,那么,在任1秒内( )